When WordPress may be infected with malware (virus or tampering), you can easily use a plugin to inspect and remove malware.
The following is a list of the main types of malware behavior on websites and malware scanning and disinfection plug-ins.

Major site malware behavior when WordPress is infected with malware.

Administration page gives 404 or 403 errors and cannot log in

It is possible that a hacker has rewritten the HTACCESS to prevent access to the administration screen, or has changed the password for administrative privileges.

The provider or server management company has notified us that the server is infected with malware.

The server company may have detected a malware infection and forced the site’s infected files to 000 write permissions or prevented access to the site’s folders.
In this case, the provider often contacts you by e-mail.

When I try to access your web site, I get a browser warning

If a malware infection is left unchecked, the site may be on a list of dangerous sites and a warning may appear on your browser as an infected site, making it inaccessible.

A warning appears in Google Search Console that the site has been hacked.

Google Search Console is a service provided by Google that mainly provides information on keyword searches for websites.

A product page that you do not remember is trapped in your site’s search results.

If a search engine shows a large number of pages that you do not recognize when you search for your site, and the pages are from your domain, the server may have been tampered with by a hacker and is hosting the incorrect pages.
In this case, the number of accesses may decrease drastically.

The HTML code contains invalid JavaScript.

If a website has been tampered with, forcing visitors to go to another site when they access the site or click on a link, malformed embedded JavaScript is used.
In this case, the number of accesses may decrease drastically.

Website operation becomes extremely slow or the display is corrupted.

Malware code is often of low quality and may not work properly, making the site extremely slow or corrupting the layout due to malformed embedded code.

Easily inspect and remove WordPress malware with plug-ins.

WordPress Doctor has released a plugin that allows you to easily scan for malware (viruses and tampering) from the WordPress administration screen and includes an automatic removal function.

To date, we have contributed to the removal of malware from over 30,000 websites.
We hope you will give it a try.

Free WordPress:Malware Scan & Security Plug-in [Malware and Virus Detection and Removal].